The invention relates to a hydraulic spring having a damper, especially as a primary spring for use in rail vehicles as disclosed in German patent 4,446,800 wherein the spring is referred to as a xe2x80x9chydraulically damping elastic bearingxe2x80x9d.
The bearing, which is described in German patent 4,446,800 with respect to FIG. 1a thereof, includes a spring element 1 which, on the one hand, is connected to a connecting part 11 and, on the other hand, is fixedly connected to a cylindrical housing 3. The spring element 1 is especially vulcanized to the cylindrical housing 3. The cylindrical housing 3 is secured with threaded fasteners to the other connecting part 12. The cup-shaped bearing cover 13 is connected as one piece to the connecting part 12 and has air compensating bores 13.1. The hydraulic damping system of the bearing comprises the work chamber 6 and the compensating chamber 7 closed off to the ambient by the highly flexible elastic compensating membrane 2 as well as a connecting channel 4 formed in the partition wall 5. The enclosed hydraulic liquid can flow throttled back and forth through the connecting channel 4 between the two chambers.
According to the state of the art, the partition wall 5, which is arranged within the elastic bearing, includes a cylindrical edge surface in which a screw-shaped slot is formed. Together with the housing 3, the slot, which is formed in the cylindrical edge surface, forms a channel 4 which connects the two hydraulic chambers 6 and 7 with each other.
The manufacture of the slot in the cylindrical edge surface is relatively cost intensive. The cylindrical edge requires a certain space in elevation for accommodating the same because of its axial height and this height cannot be used as a path for spring deflection. An adjustment of the damping to the particular masses to be suspended is not possible with the known connecting channel (damping channel 4).
It is an object of the invention to further develop the known hydraulic spring and it is especially an object of the invention to provide a damping element which is cost effective and requires a low structural elevation for accommodating the same.
The hydraulic spring of the invention includes: a rubber elastic spring element defining a spring axis; a highly flexible elastic compensating membrane; the rubber elastic spring element and the compensating membrane conjointly closing off a volume; a partition wall partitioning the volume into a work chamber delimited by the spring element and a compensating chamber delimited by the elastic compensating membrane; the chambers being changeable in volume and filled with hydraulic fluid; the partition wall having at least one connecting channel to permit a flow of the hydraulic fluid between the chambers during the operation of the hydraulic spring; an outer ring vulcanized to the spring element; the partition wall having a planar configuration and extending transversely to the spring axis; and, the connecting channel extending planar-like within the partition wall and having a first end opening into the work chamber and a second end opening into the compensating chamber.
According to a feature of the invention, a damping channel is disposed in a single plane arranged transversely to the spring axis. From this, a very low structural elevation results, that is, either the structural elevation, which is needed for damping channels, can be used for an expanded spring path or, for the same spring path, the spring can be constructed overall to be smaller.
An adequate flow length can be realized by a spirally-shaped configuration of the damping channel, which conducts hydraulic liquid and is configured to be planar, so that no compromises with respect to the damping action must be made.
Not only with respect to the channel is there sufficient play; rather, several connecting channels can be provided which are arranged offset to each other in the plane so that the individual flow paths are connected parallel to each other. By allocating the throttle to several individual channels, the channels can be configured to have different lengths and different cross sections. In this way, a significantly more broad banded damping can take place without the maximum damping becoming less.
Furthermore, several connecting channels can be arranged in several planes. In this way, any desired size damping action can be realized.
The connecting channels are preferably built up with the aid of two discs provided with respective slots orientated toward each other (throttle upper part and throttle lower part). The two discs conjointly define a partition wall.
The two discs define the hydraulic channel and can be rotated in mutually opposite directions. In this way, the effective cross section can be varied and one can adjust the damping characteristic.
Finally, the damping characteristic can be further influenced by a selection of the coarse and fine structures of the channel surface.